A number of differential gearing systems have been devised to achieve high speed reduction ratios where low speed high torque outputs are needed. Representative of such approaches are the "Rota-Mission" manufactured and sold by Plessey Dynamics of Union, N.J., and an epicyclic gear reducer manufactured and sold by Sumitomo Machinery Corp. of Osaka, Japan. A problem inherent in such mechanisms is that the intermeshing action from direct engagement of the gears tends to generate heat losses as a result of the sliding action of the gear teeth. In non-differential axial gear systems, this problem is avoided since the gear teeth which move at high speeds encounter relatively small forces, and the gear teeth on the output side of the reducer which encounter high forces will operate at low speeds. Other devices have been devised in an effort to overcome the problem of heat losses, such as, by the use of rolling elements between the interfacing gear teeth. Representative of this approach is U.S. Pat. No. 2,874,594 to E. V. Sundt. In Sundt, an eccentric is carried by a rotating shaft for rotation therewith and an oscillating member is rotatably mounted on the eccentric. The oscillating member is provided with a ring of teeth and a gear member is rotatably mounted concentrically with the shaft and provided with teeth in meshing relation with the ring of teeth on the oscillating member. A plurality of balls or rollers are movably carried by one of the members for movement along the teeth of that member and are interpositioned between the teeth and the teeth of the other member in order to rollingly transmit torque from the oscillating member to the gear member. Multiple speed reduction can also be achieved by controlling the rotation of the oscillating member with respect to the eccentric by another ring of teeth on the oscillating member which meshes with teeth on another gear. Again, rolling elements are interposed between the second set of teeth so as to control the rotation of the oscillating member with respect to the eccentric. However, the use of an eccentric member makes such systems difficult to balance, particularly at high speeds; and the concentricity between the gear surfaces imposes definite limitations with respect to size and efficiency.
Wobble plates have been employed for numerous motion-transmitting applications. For instance, by positioning the wobble plate on a rotating shaft, its axial or wobbling movement can be transmitted to impart that movement to reciprocate a piston in a cylinder or otherwise convert the rotary motion of the shaft into some form of linear or axial motion. In U.S. Pat. No. 2,836,985 to A. M. Maroth, a series of balls are sandwiched between a pair of cam plates for the purpose of converting rotary motion of a nut into linear motion of a screw, the intended function being to cause the cam plates to be moved in an axial direction as the balls successively advance between the crests and troughs along the wavy surface of the cam plate. A more recent patent to Maroth, U.S. Pat. No. 3,094,880, establishes speed reduction by axial movement imparted to a wobble plate by rolling movement of balls between the corresponding number of crests and valleys which axial movement is then converted by a wobble plate into rotational movement of a cam fixed on the output shaft of the assembly. Neither of the Maroth patents establishes speed reduction by selectively varying the relative number of gear teeth on a wobble plate with respect to another gear in achieving a predetermined speed reduction or torque output.